Question: $ F = \left[\begin{array}{rrr}1 & 0 & 0 \\ 2 & 1 & 0 \\ 0 & 0 & 1\end{array}\right]$ What is $ F^{-1}$ ?
Answer: $ = \left[\begin{array}{rrr}1 & 0 & 0 \\ -2 & 1 & 0 \\ 0 & 0 & 1\end{array}\right]$